Spin Injection Assisted Magnetic Recording

ABSTRACT

A spin injection assisted magnetic recording structure is disclosed wherein a ferromagnetic (FM) layer and at least one spin preservation (SP) layer are formed between a main pole (MP) trailing side and a write shield (WS). Current (Ia) flows between the MP and WS, or is injected into the FM layer. As a result, the spin polarized electrons from the FM layer, which flow across one or two SP layers to generate a magnetization that enhances one or both of a local WS magnetization and return field, and a local MP magnetization and write field, respectively. A lead to the FM layer may be stitched to enable lower resistance and improve reliability. The FM layer may be recessed from the ABS to allow more overlap with the SP layer for lower current density while maintaining performance. Higher linear density and area density capability, and better reliability are achieved.

RELATED PATENT APPLICATIONS

This application is related to the following: U.S. Pat. No. 10,325,618;and Docket #HT18-020, Ser. No. 16/197,586, filed on Nov. 21, 2018;assigned to a common assignee, and herein incorporated by reference intheir entirety.

TECHNICAL FIELD

The present disclosure relates to a design for a spin injection assistedmagnetic recording structure wherein a ferromagnetic (FM) layer adjoinsone or two spin preserving (SP) layers in a write gap (WG), and acurrent is injected across the FM layer and at least one SP layer, andinto one or both of a main pole (MP) and write shield (WS) to improve alocal magnetic field and field gradient at one or both of a MP/WGinterface and a WG/WS interface, respectively, thereby increasing lineardensity capability and area density capability (ADC) for perpendicularmagnetic recording (PMR) applications.

BACKGROUND

As the data areal density in hard disk drive (HDD) writing increases,write heads and media bits are both required to be made in smallersizes. However, as the write head size shrinks, its writabilitydegrades. In particular, perpendicular magnetic recording (PMR)performance is limited by the saturation magnetization (Ms) of availablemagnetic materials. To improve writability, new technology is beingdeveloped that assists writing to a media bit. Two main approachescurrently being investigated are thermally assisted magnetic recording(TAMR) and microwave assisted magnetic recording (MAMR). The latter isdescribed by J-G. Zhu et al. in “Microwave Assisted Magnetic Recording”,IEEE Trans. Magn., vol. 44, pp. 125-131 (2008). MAMR uses a spin torquedevice to generate a high frequency field that reduces the coercivefield of a medium bit thereby allowing the bit to be switched with alower main pole field. A third approach called STRAMR (spin torquereversal assisted magnetic recording) relies on spin torque to reverse amagnetization in a flux generating layer (FGL) in the write gap toincrease reluctance and force more magnetic flux from the MP at the ABS.STRAMR is described in U.S. Pat. No. 6,785,092.

Spin transfer (spin torque) devices are based on a spin-transfer effectthat arises from the spin dependent electron transport properties offerromagnetic-spacer-ferromagnetic multilayers. When a spin-polarizedcurrent passes through a FM1/NM/FM2 multilayer in a CPP (currentperpendicular to plane) configuration where FM1 and FM2 are first andsecond FM layers and NM is a non-magnetic spacer, the spin angularmoment of electrons from FM1 that is incident on FM2 interacts withmagnetic moments of FM2 near the NM/FM2 interface. Through thisinteraction, the electrons transfer a portion of their angular momentumto FM2. As a result, spin-polarized current can switch the FM2magnetization direction or enhance FM2 magnetization depending on thecurrent density. Spin transfer devices are also known as spintronicdevices and may have ferromagnetic (FM) layers with a perpendicularmagnetic anisotropy (PMA) component where magnetization is alignedsubstantially perpendicular to the plane of the FM layer. These deviceshave an advantage over devices based on in-plane anisotropy in that theycan satisfy the thermal stability requirement but also have less limitson cell aspect ratio. As a result, spintronic structures based on PMAare capable of scaling for higher packing density, which is a keychallenge for future MRAM (Magnetoresistive Random Access Memory) andspin torque transfer (STT)-MRAM applications, and for other spintronicdevices such as microwave generators and assist structures for PMR.

Related U.S. patent application Ser. No. 16/197,586 discloses a magneticflux guiding device that is a STRAMR approach. STRAMR devices typicallyrequire a high current density to flip a magnetization in a FM layer inthe WG, and this issue is substantially overcome by placing spinpolarization (SP) layers on each side of the FM layer so that anadditive spin torque on the FM layer magnetization is generated to allowa reduced current density. However, a new assist design is desired thatdoes not rely on spin flipping to enhance the write field, and hasflexibility in increasing one or both of a local magnetic field andfield gradient at the main pole/WG interface and at the WG/write shieldinterface thereby improving linear density and areal density capability.

SUMMARY

One objective of the present disclosure is to provide a PMR writerwherein a spin injection assisted magnetic recording (SIAMR) device isformed in a write gap (WG) and enables spin polarized electrons to flowinto one or both of a write shield at a SIAMR/WS interface and into a MPat a MP/SIAMR interface thereby enhancing the return field and writefield, respectively, to improve linear density and ADC.

A second objective of the present disclosure is to provide a SIAMRdevice according to the first objective that also provides improvedreliability compared with conventional PMR writers with MAMR capability.

According to one embodiment of the present invention, these objectivesare achieved with a PMR writer design wherein a SIAMR device comprises aFM layer and at least one adjoining spin preserving (SP) layer in the WGbetween a MP and a WS. In a first embodiment, the SIAMR device furtherincludes a pair of so-called spin killing layers made of Ta, W, Pt, Ru,Ti, or Ir on a side of the FM layer that is opposite to the FM side thatadjoins the SP layer. The SP layer contacts the WS, and applied currentflows from the MP to WS so that spin polarized electrons from the FMlayer provide a magnetization that enhances a local WS field proximateto the SP/WS interface and a return field in the WS. In an alternativeembodiment, when the SP layer contacts the MP and applied current(I_(a)) flows from the WS through the FM layer and SP layer into the MP,I_(a) produces a magnetization that enhances a local MP field proximateto the MP/SP interface, and the write field. There are leads from the MPand WS that are connected to a direct current (dc) source to enableI_(a) to be applied across the SIAMR device during a write process.

According to a second embodiment, the features of the first embodimentare retained except the spin killing layers are replaced with adielectric (WG) layer, and I_(a) is applied through a lead to the FMlayer and across the SP layer to the WS. In both of the first and secondembodiments, each of the FM and SP layers has a front side at the airbearing surface (ABS), and the SP layer has a backside at a WS throatheight (TH). A backside of the FM layer is typically at a heightsubstantially greater than the WS TH in the second embodiment. The FMlayer may be a single layer or multilayer that is comprised of one ormore of Fe, Co, CoFe, NiFe, CoFeNi, and alloys thereof such as CoB, FeB,CoFeB, and CoFeNiB, or alloys with one or more of Ta, Zr, and Cr such asCoTaZr. The SP layer is a material comprised of one or more of Cu, Au,Ag, Ru, Cr, and Al while the dielectric (WG) layer may be an oxide ornitride of Al, Mg, Si, Ti, Ta, Hf, or Zr.

A third embodiment retains all the features of the second embodimentexcept the backside of the SP layer is extended to a height greater thanthe WS TH to enable greater current density in the spin polarizedcurrent through the SP layer.

According to a fourth embodiment that is a modification of the thirdembodiment, a front side of the FM layer is recessed to the WS TH, forexample, to allow lower current density between the FM and SP layersbecause greater overlap of the two layers is possible in the cross-trackdirection outside the tight confines of the WG proximate to the ABS.Therefore, improved reliability is expected since lower current densitymeans lower risk of electromigration of metals or alloys within the FMand SP layers.

In a fifth embodiment, the dielectric layer adjoining one side of the FMlayer in the fourth embodiment is replaced with a first SP layer (SP1)such that spin polarized current from the FM layer flows through SP1 tothe MP and through a second SP layer (SP2) to the WS to enhancelocalized MP and localized WS magnetization, respectively, therebyimproving the write field and return field. Optionally, one or both ofthe FM layer front side is at the ABS, and the SP1 and SP2 backsides areat the WS TH.

According to a sixth embodiment, any of the second through fifthembodiments is modified to use a stitched lead between the dc source andthe FM layer. Thus, a back portion of the FM layer may be stitched to aSP material or to a spin killing material. As a result, the leadresistance is lowered, which in turn reduces operating temperature toimprove reliability.

In the seventh embodiment, the FM layer in the second embodiment isomitted and the SP layer adjoins both of the WS and MP so that whenI_(a) is applied from the MP to the WS, a portion of the MP proximate tothe MP/SP interface serves as the FM layer, which spin polarizes I_(a).A first portion of the SP layer proximate to the MP trailing side ispreferably recessed beyond the WS TH to avoid reducing MP magnetizationproximate to the ABS, and a second portion of the SP layer adjoining theWS has a front side at the ABS, and a backside at the same height as thefirst portion.

A process sequence is also provided for forming a SIAMR stack of layersaccording to an embodiment of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a head arm assembly of the presentdisclosure.

FIG. 2 is side view of a head stack assembly of the present disclosure.

FIG. 3 is a plan view of a magnetic recording apparatus of the presentdisclosure.

FIG. 4 is a down-track cross-sectional view of a combined read-writehead with leading and trailing loop pathways for magnetic flux return tothe main pole in the PMR writer according to an embodiment of thepresent disclosure.

FIG. 5 is an ABS view of a SIAMR device according to a first embodimentof the present disclosure wherein a stack comprised of two spin killinglayers, a FM layer, and a SP layer are formed on a MP trailing side andin a WG such that the SP layer adjoins a WS bottom surface.

FIG. 6A is a down-track cross-sectional view of the SIAMR device in FIG.5 where a current I_(a) is applied from the MP and across the FM and SPlayers to enhance a local WS magnetic field and WS return field.

FIG. 6B is an alternative first embodiment where the stacking order ofSIAMR device layers in FIG. 6A is reversed, and I_(a) is applied fromthe TS and across the FM and SP layers to enhance a local MP magneticfield and write field.

FIG. 7 is a down-track cross-sectional view where the spin killinglayers in FIG. 6A are replaced with a dielectric layer and I_(a) isinjected into the FM layer and flows to the WS according to a secondembodiment of the present disclosure.

FIG. 8 is a down-track cross-sectional view depicting a third embodimentof the present disclosure wherein a backside of the SP layer in FIG. 7is extended beyond a WS throat height (TH), and I_(a) flows from the FMlayer to WS.

FIG. 9 is a down-track cross-sectional view of a fourth embodiment ofthe present disclosure wherein a front side of the FM layer in FIG. 8 isrecessed to a WS throat height.

FIG. 10 is a down-track cross-sectional view of a fifth embodiment ofthe present disclosure wherein a second SP layer is inserted between theFM layer and MP trailing side in FIG. 9 so that spin polarized currentfrom the FM layer flows through both of the first and second SP layersto the WS and MP, respectively.

FIG. 11 is a down-track cross-sectional view showing a sixth embodimentof the present disclosure that is a modification of the fifth embodimentwherein the lead to the FM layer is stitched.

FIG. 12 is a down-track cross-sectional view depicting a seventhembodiment of the present disclosure wherein the FM layer in FIG. 9 isomitted, and the SP layer has a first portion adjoining the MP that hasa recessed front side while a second portion of the SP layer contactingthe WS has a front side at the ABS.

FIGS. 13A, 14A, 16A-18A and FIGS. 19-21 are ABS views that depict asequence of steps in forming a SIAMR stack of layers between a MPtrailing side and a WS according to an embodiment of the presentdisclosure.

FIGS. 13B, 14B, and 16B are down-track cross-sectional views of theintermediate structures shown in FIGS. 13A, 14A, and 16A, respectively,and FIG. 15 is a down-track cross-sectional view showing the patterningof a FM layer.

FIG. 17B is a top-down view of the intermediate structure shown in FIG.17A that depicts a step of patterning a front portion of the SP layeraccording to an embodiment of the present disclosure.

FIG. 18B is a top-down view of the intermediate structure in FIG. 18Athat depicts a step of forming a cross-track width in the SIAMR stack oflayers according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

The present disclosure is a PMR writer with a SIAMR design wherein spinpolarized current is injected into a FM layer and then across at leastone SP layer in a WG before entering a main pole or a write shield inorder to improve linear density, reliability, and ADC. In the drawings,the y-axis is in a cross-track direction, the z-axis is in a down-trackdirection, and the x-axis is in a direction orthogonal to the ABS andtowards a back end of the writer structure. Thickness refers to adown-track distance, width is a cross-track distance, and height is adistance from the ABS in the x-axis direction. The terms “downward” and“upward” when referring to write field and return field directionalarrows in the drawings indicate a direction that is into the ABS andtoward a back end of the PMR writer for “upward”, and out of the ABS andtoward a magnetic medium for “downward”. The terms “MP field” and “writefield” may be used interchangeably. Although the exemplary embodimentsdepict a single PMR writer, the present disclosure anticipates that twoor more PMR writers may be formed on a slider and each of the PMRwriters comprises a SIAMR device described herein.

Referring to FIG. 1, a head gimbal assembly (HGA) 100 includes amagnetic recording head 1 comprised of a slider and a PMR writerstructure formed thereon, and a suspension 103 that elastically supportsthe magnetic recording head. The suspension has a plate spring-like loadbeam 222 formed with stainless steel, a flexure 104 provided at one endportion of the load beam, and a base plate 224 provided at the other endportion of the load beam. The slider portion of the magnetic recordinghead is joined to the flexure, which gives an appropriate degree offreedom to the magnetic recording head. A gimbal part (not shown) formaintaining a posture of the magnetic recording head at a steady levelis provided in a portion of the flexure to which the slider is mounted.

HGA 100 is mounted on an arm 230 formed in the head arm assembly 103.The arm moves the magnetic recording head 1 in the cross-track directiony of the magnetic recording medium 140. One end of the arm is mounted onbase plate 224. A coil 231 that is a portion of a voice coil motor ismounted on the other end of the arm. A bearing part 233 is provided inthe intermediate portion of arm 230. The arm is rotatably supportedusing a shaft 234 mounted to the bearing part 233. The arm 230 and thevoice coil motor that drives the arm configure an actuator.

Next, a side view of a head stack assembly (FIG. 2) and a plan view of amagnetic recording apparatus (FIG. 3) wherein the magnetic recordinghead 1 is incorporated are depicted. The head stack assembly 250 is amember to which a first HGA 100-1 and second HGA 100-2 are mounted toarms 230-1, 230-2, respectively, on carriage 251. A HGA is mounted oneach arm at intervals so as to be aligned in the perpendicular direction(orthogonal to magnetic medium 140). The coil portion (231 in FIG. 1) ofthe voice coil motor is mounted at the opposite side of each arm incarriage 251. The voice coil motor has a permanent magnet 263 arrangedat an opposite position across the coil 231.

With reference to FIG. 3, the head stack assembly 250 is incorporated ina magnetic recording apparatus 260. The magnetic recording apparatus hasa plurality of magnetic media 140 mounted to spindle motor 261. Forevery magnetic recording medium, there are two magnetic recording headsarranged opposite one another across the magnetic recording medium. Thehead stack assembly and actuator except for the magnetic recording heads1 correspond to a positioning device, and support the magnetic recordingheads, and position the magnetic recording heads relative to themagnetic recording medium. The magnetic recording heads are moved in across-track of the magnetic recording medium by the actuator. Themagnetic recording head records information into the magnetic recordingmedia with a PMR writer element (not shown) and reproduces theinformation recorded in the magnetic recording media by amagnetoresistive (MR) sensor element (not shown).

Referring to FIG. 4, magnetic recording head 1 comprises a combinedread-write head. The down-track cross-sectional view is taken along acenter plane (44-44 in FIG. 5) formed orthogonal to the ABS 30-30, andthat bisects the main pole layer 14. The read head is formed on asubstrate 81 that may be comprised of AlTiC (alumina+TiC) with anoverlying insulation layer 82 that is made of a dielectric material suchas alumina. The substrate is typically part of a slider formed in anarray of sliders on a wafer. After the combined read head/write head isfabricated, the wafer is sliced to form rows of sliders. Each row istypically lapped to afford an ABS before dicing to fabricate individualsliders that are used in a magnetic recording device. A bottom shield 84is formed on insulation layer 82.

A magnetoresistive (MR) element also known as MR sensor 86 is formed onbottom shield 84 at the ABS 30-30 and typically includes a plurality oflayers (not shown) including a tunnel barrier formed between a pinnedlayer and a free layer where the free layer has a magnetization (notshown) that rotates in the presence of an applied magnetic field to aposition that is parallel or antiparallel to the pinned layermagnetization. Insulation layer 85 adjoins the backside of the MRsensor, and insulation layer 83 contacts the backsides of the bottomshield and top shield 87. The top shield is formed on the MR sensor. Aninsulation layer 88 and a top shield (S2B) layer 89 are sequentiallyformed on the top magnetic shield. Note that the S2B layer 89 may serveas a flux return path (RTP) in the write head portion of the combinedread/write head. Thus, the portion of the combined read/write headstructure formed below layer 89 in FIG. 4 is typically considered as theread head. In other embodiments (not shown), the read head may have adual reader design with two MR sensors, or a multiple reader design withmultiple MR sensors.

The present disclosure anticipates that various configurations of awrite head may be employed with the read head portion. In the exemplaryembodiment, magnetic flux known as write field 70 in main pole (MP)layer 14 is generated with flowing a write current (Iw) through buckingcoil 80 b and driving coil 80 d that are below and above the MP layer,respectively, and are connected by interconnect 51. Magnetic flux 70exits the MP layer at pole tip 14 p at the ABS 30-30 and is used towrite a plurality of bits on magnetic media 140. Magnetic flux 70 breturns to the MP through a trailing loop comprised of trailing shields17, 18, PP3 shield 26, and top yoke 18 x. There is also a leading returnloop for magnetic flux 70 a that includes leading shield 11, leadingshield connector (LSC) 33, S2 connector (S2C) 32, return path 89, andback gap connection (BGC) 62. The magnetic core may also comprise abottom yoke 35 below the MP layer. Dielectric layers 10, 13, 36-39, and47-49 are employed as insulation layers around magnetic and electricalcomponents. A protection layer 27 covers the PP3 trailing shield and ismade of an insulating material such as alumina. Above the protectionlayer and recessed a certain distance u from the ABS 30-30 is anoptional cover layer 29 that is preferably comprised of a lowcoefficient of thermal expansion (CTE) material such as SiC. Overcoatlayer 28 is formed as the uppermost layer in the write head.

Referring to FIG. 5, an ABS view is depicted of the PMR writer in FIG. 4according to an embodiment of the present disclosure. The main pole (MP)has a MP tip 14 p with track width w, trailing side 14 t 1, leading side14 b 1, and two sides 14 s formed equidistant from a center plane 44-44in an All Wrap Around (AWA) shield structure. There is a write gap 16with thickness t on the MP trailing side, side gaps 15 adjoining each MPside, and a leading gap 13 below the MP leading side. Leading shield 11contacts the leading gap and a bottom surface of side shields 12 atplane 42-42. Side shields (SS) have an inner side 12 s adjoining a sidegap, and far sides 60, 61 at an outer side of the AWA shield structure.The trailing shield (TS) structure comprises a first trailing shieldhereinafter referred to as the write shield (WS) 17 with a magneticsaturation value from 19 kiloGauss (kG) to 24 kG, and with a bottomsurface 17 b on the WG except over a SIAMR stack of layers 2-6 eachhaving a width ≤½ w on each side of the center plane. WS sides 17 s areformed coplanar with WG sides 16 s on each side of the center plane. TheTS structure also includes a second TS 18 formed on the WS top surfaceand sides 17 t and 17 s, respectively, on WG sides 16 s, and on a topsurface of the side shields 12 at plane 41-41. Plane 41-41 includes theMP trailing side at the ABS. Plane 42-42 is parallel to plane 41-41, andincludes the MP leading side at the ABS. Each of the SS, leading shield,TS structure, and MP are comprised of one or more of CoFe, NiFe, andCoFeNi.

According to a first embodiment of the present disclosure, the SIAMRstack of layers has a first spin killing (SK) layer 2, non-magneticspacer 3, second SK layer 4, FM layer 5, and spin preserving (SP) layer6 sequentially formed on MP trailing side 14 t 1. The SIAMR stack oflayers has thickness t equivalent to that of WG layer 16 between plane41-41 and WS 17, and a width that is typically <w. Each SK layer is alsoknown as a non-spin preserving layer and prevents spin polarizedelectrons from the FM layer from reaching the MP trailing side, and ispreferably one of Ta, W, Pt, Ru, Ti, Ir, or Cr. The non-magnetic spaceris comprised of Ta, Ru, W, or Cr, and serves to improve the growth ofthe FM layer for better magnetic properties. The FM layer may be asingle layer or multilayer that is comprised of one or more of Fe, Co,CoFe, NiFe, CoFeNi, and alloys thereof such as CoB, FeB, CoFeB, andCoFeNiB, or alloys with one or more of Ta, Zr, Re, and Mo. The SP layeris non-magnetic and comprises one or more of Cu, Au, Ag, Ru, Cr, and Al,and is responsible for having sufficient spin diffusion length to allowspin polarized electrons (not shown) to substantially remain in theiroriginal orientation while traversing from the FM layer to WS 17 (and toMP 14 in the fifth and sixth embodiments described later).

The first embodiment is a modification of the spin flipping elementdisclosed in related U.S. Pat. No. 10,325,618. We have discovered thatby replacing a single SK layer with a stack comprised of a non-magneticspacer 3 between two SK layers 2 and 4 in the SIAMR stack of layers,performance characteristics including electrical conductivity, thermalconductivity, electro-thermal robustness, and magnetic dampingproperties are simultaneously optimized.

Referring to FIG. 6A, a down-track cross-sectional view of the firstembodiment is shown where the SIAMR stack of layers 2-6 is formedbetween MP 14 and WS 17. First SK layer 2 forms a first interface thatis also referred to as the MP/SK interface with MP trailing side 14 t 1,and SP layer 6 forms a second interface also known as the SP/WSinterface with WS bottom surface 17 b. MP local magnetization 14 m thatis adjacent to the MP/SK interface is generally in the direction of thewrite gap field flux (H_(WG)), which is from the MP trailing side to WSbottom surface. There is also a local WS magnetization 17 m adjacent tothe SP/WS interface that is substantially parallel to H_(WS). Moreover,FM layer 5 has magnetization 5 m substantially parallel to H_(WS). Otherlayers in the PMR writer are omitted in order to focus on the path ofapplied current I_(a) while writing a transition where write field 70 isoriented downward at the ABS 30-30 and into a magnetic medium (notshown), and where return field 70 b is orthogonal to the ABS and upwardinto the WS. In the exemplary embodiment, each of the SIAMR stack oflayers has a front side at the ABS, and a backside at a WS throat heighth where the WS bottom surface connects with WS side 17 s. Thus, frontsides 5 f and 6 f of the FM layer and SP layer, respectively, arecoplanar, and FM layer backside 5 e and SP layer backside 6 e are atheight h. Lead 57 carries I_(a) into MP 14 from direct current (dc)source 50 while lead 58 carries I_(a) back to the dc source from TS 17.In other embodiments (not shown), the SIAMR stack of layers may have abackside at a height unequal to h.

A key feature is that when I_(a) flows from the MP 14 to WS 17, spinpolarized current from FM layer 5 traverses the SP layer 6 and entersthe WS, and produces a magnetization (not shown) proximate to the SP/WSinterface that enhances local WS magnetization 17 m and return field 70b. I_(a) current density is less than required to flip FM magnetization5 m in STRAMR devices. Therefore, improved reliability is realizedbecause of a reduced risk of electromigration within the SIAMR metal oralloy layers. During a transition (not shown) when the write field isorthogonal to the ABS 30-30 and upward into the MP, and the directionsof I_(a), magnetizations 5 m, 14 m, and 17 m, and return field 70 b arereversed, there is no spin torque applied to local MP magnetization 14 mbecause SK layers 2 and 4 prevent spin polarized electrons from reachingthe MP.

An alternative first embodiment is depicted in FIG. 6B where the SIAMRlayers are formed in reverse stacking order on MP trailing side 14 t 1such that SP layer 6 adjoins the MP trailing side and forms a MP/SPinterface while SK layer 2 contacts the WS bottom surface 17 b and formsa SK/WS interface. This reverse SIAMR configuration is advantageous forboosting write field 70 during a transition when the write field isoriented orthogonal to the ABS 30-30 and into the MP 14, and when I_(a)is applied from the WS to MP. Here, local MP magnetization 14 m, FMmagnetization 5 m, local WS magnetization 17 m, and return field 70 bare also opposite to the direction shown in FIG. 6A. In this case, spinpolarized current from FM layer 5 traverses the SP layer and enters theMP to generate a magnetization adjacent to the MP trailing side thatenhances the local MP magnetization 14 m, and write field 70 that is inan upward direction. When the write field is reversed and I_(a) isapplied from the MP to WS, there is no spin torque produced on WSmagnetization 17 m because of the presence of SK layers 2, 4 thatprevent spin polarized electrons from reaching WS bottom surface 17 b.

Referring to FIG. 7, a second embodiment of the present disclosure isdepicted and is a modification of the first embodiment where SK layers 2and 4, and spacer 3 are replaced with WG layer 16 that is a dielectricmaterial. Furthermore, current I_(a) is injected through lead 57 andthen into a contact 59 before entering the FM layer 5 since there is nolonger a conductive pathway from MP 14 to the FM layer. The FM layerbackside 5 e is now at a height substantially greater than height h1where the MP tapered trailing side 14 t 1 connects with MP top surface14 t 2 at corner 14 c. Thus, the FM layer has a bottom surface 5 b thatfaces the MP and is separated from MP trailing side by WG layer 16, andfrom MP top surface by insulation layer 47. FM layer top surface 5 tadjoins contact 59 proximate to end 5 e. Otherwise, all aspects of theSP layer 6 are retained from the first embodiment in FIG. 6A including afront side 6 f at the ABS 30-30, and a backside 6 e at the WS TH, whichis height h. Accordingly, spin polarized electrons from the FM layertraverse SP layer 6 and generate magnetization that enhances local WSmagnetization 17 m proximate to the SP/WS interface, and return field 70b when write field 70 is out of the MP and orthogonal to the ABS 30-30,and the return field is in an upward direction. Again, linear densityand ADC are improved. When writing a transition where the write field,return field, I_(a), and magnetizations 14 m, 5 m, and 17 m arereversed, there is no enhancement to the write field because the WGlayer prevents spin polarized electrons from reaching the MP trailingside.

Referring to FIG. 8, a third embodiment of the present disclosure isillustrated and is a modification of the second embodiment in FIG. 7where SP layer backside 6 e is extended farther from the ABS 30-30 to aheight h2 where h2>h. The additional height of the SP layer 6 betweenfront side 6 f and backside 6 e is expected to allow more spin polarizedcurrent from the FM layer 5 to the SP/WS interface thereby generatinggreater magnetization to further enhance WS magnetization 17 m and writefield 70 b (with the same current density in FM layer 5) compared withthe SIAMR structure in FIG. 7. Optionally, less current density (sametotal current) in the FM layer produces an equal amount of magnetizationto enhance WS magnetization and return field compared with previousembodiments to improve device reliability. Otherwise, all features andadvantages of the second embodiment are retained in the thirdembodiment.

In FIG. 9, a fourth embodiment of the present disclosure is shown wherethe SIAMR structure in FIG. 8 is modified by recessing FM layer frontside 5 f to height h. Thus, WG layer 16 fills the entire space betweenthe ABS 30-30 and FM layer front side, and SP layer 6 is the only SIAMRlayer exposed at the ABS and in contact with WS 17. This design isexpected to allow lower current density between the FM layer 5 and SPlayer since this scheme allows a greater overlap of the aforementionedlayers in the cross-track direction in embodiments where there is alarger WG cavity (not shown) at a height greater than h than between theABS and the WS TH at height h. As a result, there is a significantimprovement in reliability at the same performance compared with earlierembodiments where the write field 70 is in a downward direction out ofthe ABS, the return field 70 b is upward from the ABS, and I_(a) is fromthe FM layer and across the SP layer into the WS 17 to enhance local WSmagnetization 17 m and the return field.

Referring to FIG. 10, a fifth embodiment of the present disclosure isdepicted and is a modification of the embodiment in FIG. 9 where aportion of the WG layer 16 adjoining MP trailing side 14 t 1 is replacedwith a first SP layer (SP1) 6 a having a backside 6 e 1 at height h2,and a front side 6 f 1 at the ABS 30-30. Thus, the SP1 forms a MP/SP1interface with the MP trailing side, and adjoins a portion of FM layerbottom surface 5 b. The second SP layer (SP2) 6 b (former SP layer 6 inFIG. 9) contacts a portion of FM layer top surface 5 t, and forms aSP2/WS interface with WS bottom surface 17 b. The SP2 has a front side 6f 2 at the ABS, and a backside 6 e 2 at height h2. There is a firstreturn lead 58 a between TS 17 and dc source 50 that carries currentI_(b), and a second return lead 58 b between MP 14 and the dc sourcethat carries I_(a). In this embodiment, lead 57 is connected to contact59, which injects (I_(a)+I_(b)) from the dc source to FM layer 5. Inalternative embodiments (not shown) where the FM layer front side 5 f ismoved forward to the ABS, one or both of SP1 and SP2 backsides 6 e 1 and6 e 2, respectively, may also be moved forward to height h, ormaintained at height h2.

An advantage of the SIAMR layout in the fifth embodiment compared withprevious embodiments is that write field 70 and return field 70 b aresimultaneously enhanced as a result of spin polarized current from FMlayer 5 through SP1 6 a and into MP tip 14 p to generate magnetization(not shown) that enhances local MP magnetization 14 m and the writefield, and from the FM layer through SP2 6 b and into WS 17 to producemagnetization that increases local WS magnetization 17 m and the returnfield.

Note that the fifth embodiment provides similar benefits when thedirection of the write field 70, return field 70 b, and magnetizations 5m, 14 m, and 17 m are reversed (not shown) because I_(a) and I_(b) aremaintained in the same direction. Thus, spin polarized electronstraversing through SP1 6 a from FM layer 5 will continue to enhancelocal MP magnetization 14 and the write field, and spin polarizedcurrent through SP2 6 b will continue to increase local WS magnetization17 m and the return field.

Referring to FIG. 11, a sixth embodiment of the present disclosure isshown that is a modification of the fifth embodiment where SP1 and SP2front sides 6 f 1 and 6 f 2, respectively, as well as FM layer frontside 5 f are at the ABS 30-30, and where SP1 and SP2 backsides 6 e 1 and6 e 2, respectively, are at height h2. A key feature is that lead 57from the dc source 50 to FM layer 5 in FIG. 10 is now stitched andcomprised of a SP material or spin killing material in stitched layer 7having one end at contact 59, and an opposite end that overlaps a topsurface 5 t of the FM layer proximate to end 5 e. Accordingly, a portionof stitched layer bottom surface 7 b adjoins the FM layer top surface.The stitched lead is advantageously employed to reduce the leadresistance and thereby lower temperature in the SIAMR device to improvereliability. It should be understood that the lead modificationdescribed for the sixth embodiment may be applied to any of the secondthrough fifth embodiments with similar benefits. In alternativeembodiments (not shown) where the FM layer has a front side at the ABS,one or both of SP1 6 a and SP2 6 b may have a backside at height h.

According to a seventh embodiment shown in FIG. 12, the SIAMR device inFIG. 7 is modified with the removal of FM layer 5 such that a single SPlayer extends from the MP trailing side 14 t 1 to the WS bottom surface17 b. Thus, a first portion 6 a of the SP layer has a recessed frontside 6 f 1 at height r that may be proximate to the WS TH, a backside 6e at height h2, and forms a MP/SP interface with MP trailing side.Preferably, height r is from 1 nm to 20 nm and slightly larger than theeffective throat height on the trailing shield, and h2 can be from 10 to200 nm larger than r from the ABS 30-30. In the exemplary embodiment,the MP trailing side connects with MP top surface 14 t 2 at corner 14 cthat is at height h1 from the ABS where h1>h2. A second portion 6 b ofthe SP layer has backside 6 e at height h2, a front side 6 f 2 at theABS, adjoins first portion 6 a between height r and height h2, and formsa SP/WS interface with WS bottom surface 17 b. The first portion of SPlayer is recessed from the ABS so that local MP magnetization 14 mproximate to the ABS is not reduced. Note that lead 57 now connects dcsource 50 with MP 14. Here, the MP proximate to the MP trailing sideserves as the FM layer which spin polarizes I_(a) that flows from the MPand across the SP layer and into the WS 17. Similar to previousembodiments, the spin polarized electrons produce a magnetizationproximate to the WS bottom surface that enhances local WS magnetization17 m and return field 70 b.

For all embodiments, the advantage of injecting spin polarized electronsfrom the FM layer across the SP layer and into one or both of the MP andWS generates magnetization at the MP/SP interface and SP/WS interface,respectively, that increases local magnetization at one or both of theinterfaces and enhances one or both of the write field and return fielddepending on the direction of the current flow (except in the fifth andsixth embodiments). As a result, the PMR writer has improved performancebased on greater linear density and higher ADC. Furthermore, a PMRwriter having a SIAMR structure in the WG is expected to exhibit greaterreliability because a lower current density for I_(a) is required thanin PMR writers employing a STRAMR device in the WG.

A process sequence for fabricating a magnetic flux guiding device in aWG and with a front side at the ABS has been described in relatedHT18-020. A similar sequence of steps may be used to form a SIAMR stackof layers having a width w in a WG, and a backside at a WS TH as shownin the first embodiment.

A process sequence for fabricating the SIAMR device of the secondthrough fourth embodiments is illustrated starting at FIG. 13A. Thepartially formed writer structure including MP tip 14 p that adjoinsside gaps 15 and leading gap 13 is provided according to a conventionalprocess sequence. Side shield top surfaces 12 t are coplanar with atrailing edge of the MP tapered trailing side 14 t 1 at plane 41-41,which is slightly offset from being orthogonal to the subsequentlyformed ABS plane. FIG. 13B shows the down-track cross-sectional view atplane 44-44 in FIG. 13A. MP tapered trailing side 14 t 1 has a taperangle δ (generally greater than 0 degrees) and is coplanar with atapered front side 47 f of insulation layer 47 made of AI₂O₃ or SiO₂that is formed on MP top surface 14 t 2. Tapered front side connectswith dielectric layer top surface 47 t that is above and essentiallyparallel to the MP top surface. Note that the eventual ABS, hereinafterreferred to as ABS plane 30-30, is not determined until a lappingprocess is performed after all layers in the PMR writer structure areformed.

Referring to FIG. 14A, the next step in the fabrication process issequential deposition of WG layer 16 and FM layer 5 on MP taperedtrailing side 14 t 1. FIG. 14B shows that the WG layer and FM layercontinue toward a back end of the writer structure and are also formedon insulation layer 47.

As shown in FIG. 15, a first photoresist layer is coated on FM layer 5,and then exposed with the use of a chrome on quartz mask, for example,and developed with a photolithography process to form photoresist mask52 having a front side 52 f that is recessed to height h from the ABSplane 30-30 and thereby forming an opening 53 a that exposes a portionof FM layer top surface 5 t. Note that opening 53 a may be omitted whenforming a FM layer with a front side at the ABS as in the second andthird embodiments. A second opening 53 b is also formed during thephotoresist patterning process. As a result, photoresist mask backside52 e is formed above MP top surface 14 t 2, and will be used to define aFM layer backside in a subsequent step.

In FIG. 16A, an ABS view is shown after a reactive ion etch (RIE) or ionbeam etch (IBE) process is employed to transfer openings 53 a, 53 bthrough the FM layer 5 and stop on WG layer top surface 16 t.Thereafter, photoresist mask 52 is removed by a conventional method.FIG. 16B depicts a down-track cross-sectional view of the intermediatestructure in FIG. 16A. The FM layer now has a front side 5 f that isrecessed to height h from the ABS plane 30-30, and a backside 5 e aboveMP top surface 14 t 2.

Referring to FIG. 17A, an additional WG layer 16 a is optionallydeposited on exposed portions of WG layer 16 between FM layer front side5 f and the ABS plane, and behind FM layer backside 5 e. In theexemplary embodiment, the WG layers 16, 16 a are made of the samedielectric material and shown hereinafter as a single WG layer 16. Then,SP layer 6 is deposited on the FM layer (not shown) and on the WG layer.A sputter deposition or ion beam deposition tool may be used to depositeach SIAMR layer including the FM layer 5 and SP layer. A secondphotoresist is coated and then exposed with the aid of another mask anddeveloped by a photolithography process to yield photoresist mask 54having a full width w1 between sides 54 s that are coplanar with sides60, 61 of the AWA shield structure described previously.

FIG. 17B shows a top-down view of the intermediate structure in FIG. 17Awhere the underlying MP has sides indicated by the dashed line 14 s.Dashed line 14 x is between corners 14 c and represents the interfacewhere the MP tip portion 14 p adjacent to the MP trailing side 14 t 1meets the back portion of MP 14 below MP top surface 14 t 2. Corner 14 cis also shown in a down-track cross-sectional view in FIG. 9. Returningto FIG. 17B, backside 54 b of the second photoresist mask 54 is atheight h2 where h2>h and will be used in a later step to define abackside of SP layer 6. Photoresist mask front side 54 f may be at theABS plane 30-30 or on an opposite side (not shown) of the ABS plane withrespect to backside 54 b.

FIG. 18A depicts the intermediate structure in FIG. 17A after a RIE orIBE step is performed to transfer the shape in second photoresist mask54 through exposed portions of SP layer 6 and stopping on FM layer 5thereby forming a SP layer backside 6 e at height h2 (FIG. 18B). Theresulting opening (not shown) behind the SP layer is refilled with WGlayer 16. The second photoresist mask is removed. Next, a thirdphotoresist is coated and then exposed with a new mask and developed toform a third photoresist mask 56 having width w and sides 56 s that areequidistant from center plane 44-44. Openings 55 are formed that exposeportions of SP layer top surface 6 t 1 at distances greater than ½ wfrom the center plane. Photoresist mask front side 56 f may be on anopposite side of plane 30-30 than MP sides 14 s since the ABS is notdetermined until a lapping process at the end of the fabricationsequence.

Referring to FIG. 19, a RIE or IBE process is performed to transferopenings 55 through exposed portions of WG layer 16, and FM layer 5before stopping on SS top surface 12 t and side gap 15 on each side ofcenter plane 44-44. As a result, SP layer 6 has a constant width w fromplane 30-30 to a backside (not shown) at height h2, and FM layer 5 haswidth w from front side that is at height h to a backside 5 e describedearlier. Thereafter, WG layer 16 is deposited on SS top surface and theside gap to thickness t. The third photoresist mask is removed with aconventional method.

Referring to FIG. 20, WS 17 is deposited on WG layer 16 and on SP layer6. Next, a fourth photoresist layer is coated on the WS and is exposedwith a fourth mask and developed to generate a fourth photoresist mask58 having width w2 where w2>w, and sides 58 s that are equidistant fromcenter plane 44-44. Openings 57 adjacent to sides 58 s expose a portionof WS top surface 17 t.

FIG. 21 depicts the intermediate structure in FIG. 20 after a RIE or IBEis performed to transfer openings 57 through WS 17 and WG layer 16, andstopping on SS top surface 12 t. After the fourth photoresist mask isremoved with a conventional process, the second TS 18 is plated on SStop surface 12 t, WS top surface 17 t, and adjoins WG sides 16 s and WS17 s. Thereafter, a well known sequence of steps is followed to formoverlying layers in the PMR writer. Finally, a lapping step is used toform the ABS at plane 30-30 described previously.

While the present disclosure has been particularly shown and describedwith reference to, the preferred embodiments thereof, it will beunderstood by those skilled in the art that various changes in form anddetails may be made without departing from the spirit and scope of thisdisclosure.

1. A spin injection assisted magnetic recording (SIAMR) structure,comprising: (a) a main pole (MP) that is configured to generate amagnetic (write) field which is directed orthogonal to an air bearingsurface (ABS) and through a MP tip at the ABS; (b) a write shield (WS)with a side at the ABS through which a return field passes orthogonal tothe ABS, and having a bottom surface that faces a MP trailing side; and(c) a SIAMR stack of layers formed in a write gap (WG) wherein a firstlayer contacts the WS bottom surface, and a second layer contacts the MPtrailing side, wherein the SIAMR stack of layers comprises: (1) aferromagnetic (FM) layer having a magnetization substantially in adirection of a WG field flux between the MP and WS; (2) a spinpreservation (SP) layer that adjoins a first side of the FM layer, andis either the first layer that conducts spin polarized current from theFM layer into the WS at the WS bottom surface, or is the second layerthat conducts spin polarized current from the FM layer into the MPtrailing side, and wherein the SIAMR stack of layers is configured sothat when a current (Ia) is injected from a source into the FM layerthrough a lead that excludes the MP and TS, spin polarized electronsflow across the SP layer to generate a magnetization proximate to the MPtrailing side that enhances a local MP magnetization and the write fieldwhen the SP layer is the second layer, or produces a magnetizationproximate to the WS bottom surface that enhances a local WSmagnetization and the return field when the SP layer is the first layer;and (3) the other of the first layer or second layer that contacts asecond side of the FM layer opposite to the FM layer first side, anddoes not allow spin polarized current to flow to the MP or TS. 2.(canceled)
 3. The SIAMR structure of claim 1 wherein the FM layer is asingle layer or multilayer comprised of one or more of Fe, Co, CoFe,NiFe, CoFeNi, and alloys thereof including CoB, FeB, CoFeB, and CoFeNiB,or alloys with one or more of Ta, Zr, Re, and Mo.
 4. The SIAMR structureof claim 1 wherein the SP layer is one or more of Cu, Au, Ag, Ru, Cr,and Al. 5-6. (canceled)
 7. A head gimbal assembly (HGA), comprising: (a)a magnetic recording head that comprises the SIAMR structure of claim 1;and (b) a suspension that elastically supports the magnetic recordinghead, wherein the suspension has a flexure to which the magneticrecording head is joined, a load beam with one end connected to theflexure, and a base plate connected to the other end of the load beam.8. A magnetic recording apparatus, comprising: (a) the HGA of claim 7;(b) a magnetic recording medium positioned opposite to a slider; (c) aspindle motor that rotates and drives the magnetic recording medium; and(d) a device that supports the slider, and that positions the sliderrelative to the magnetic recording medium. 9-36. (canceled)
 37. TheSIAMR structure of claim 1 wherein the SP layer has a backside at a WSthroat height (TH), and wherein the FM layer has a front side at theABS, and a backside at a height substantially greater than the WS throatheight.
 38. The SIAMR structure of claim 1 wherein the second layer is adielectric (WG) layer that prevents spin polarized current from reachingthe MP trailing side.
 39. The SIAMR structure of claim 1 furthercomprised of a contact on the FM layer, wherein the contact connects theFM layer to the lead from the source.